Progress toward poliomyelitis eradication in Kano State, Nigeria, 2010 - 2017

Introduction Kano State in Northern Nigeria was a major source of Wild Polio Virus (WPV) cases in Nigeria up until 2015. In 2009, the State reported 168 WPV cases out of the 388 reported nationally. This paper characterizes the progress made by Kano State in polio eradication. Methods In December 2017, we conducted a descriptive review of Routine Immunization (RI) from both the District Vaccine Data Management Tool (DVD-MT) and District Health Information System (DHIS2) from 2010 to 2017. Also, we reviewed the Acute Flaccid Paralysis (AFP) and Supplementary Immunization Activities (SIAs) data reported for Kano State from 2010 to 2017. Also, we obtained the number of reported WPV cases by serotypes. Results From 2010 to 2017, a total of 65 confirmed WPV cases were reported in Kano State. Of these, 58 (89%) were WPV1 and 7 (11%) WPV3. Almost half of these cases were reported in 2012 from 14 LGAs. The number of reported cases fell to 15 (23%) in 10 LGAs in 2013, and further decreased to 5 (8%) in four LGAs in 2014. No new WPV cases have been detected in Kano since 2015. During the same period, 23 circulating Vaccine Derived Polio Viruses (cVDPV2) cases were reported in Kano. Specifically, 10 LGAs reported 10 cases in 2011. Three LGAs reported three cases in 2012, while eight LGAs reported 10 total cases in 2014. During the 2010 to 2017 period 61 SIAs were conducted. Conclusion Kano State made progress toward polio eradication. Sustained eradication efforts, in form of high quality RI, SIAs and AFP surveillance are necessary to avert possible importation from 2016 polio resurgence in nearby Borno State, Nigeria.


Introduction
In 1988, the World Health Assembly resolved to eradicate poliomyelitis [1]. In 2012, the Nigerian government activated an emergency operations center and implemented a national emergency action plan to eradicate polio [2]. From 2012 to 2015, Nigeria witnessed drastic reduction in the number of WPVs, from 122 cases reported in 2012 to six in 2014, [3]. The six wild poliovirus type 1 (WPV1) cases in 2014 were geographically limited to five in Kano and one in Yobe state [3]. After twenty-three months without detection of WPV1, four cases were detected in Borno state [4][5][6].      (Table 6).

Discussion
Evidence of progress towards poliomyelitis eradication in Kano State from 2010 to 2017 include a reduction of overall WPV and cVDPV2 incidence, and decline in number of WPV isolates from environmental samples and narrowing of geographic distribution of cases. However, persistence of polio compatible cases throughout the years indicates surveillance gap and call for urgent action by the GPEI stakeholders in the State. The occurrence of polio-compatible cases indicates surveillance failure and therefore the system may not be fully relied upon to exclude with certainty the existence of areas of poliovirus transmission [7,8].  (Table 3).    Our study has two major limitations. First, the Routine Immunization performance was based on administrative coverage, due to inaccurate estimate of the target population the coverage might be overestimated. Secondly, the results we have presented in this study are based on secondary data analysis which could entail missing data and only data captured by the system, there might be other unreported cases in the community.
Although progress was made in polio eradication in Kano State, however, the risk of importation or re-introduction of poliovirus from endemic States such as Borno remains a major threat for Kano since it is a major commercial hub in Northern Nigeria with daily influx of people across the country. Moreover, insecurity and cattle rustling in some parts of Nigeria has resulted in the influx of nomadic Fulanis population to Kano. Therefore sustained AFP surveillance in children younger than 15 years is critical.

Conclusion
Kano State has not reported any WPV or cVDPV2 cases in three years. The success recorded could be attributable to SIA, and surveillance quality occasioned by high level political and traditional leadership commitment. The establishment of EOC has provided a better coordination between Government and partners oversight to polio eradication activities at all levels.

Competing interests
The authors declare no competing interests. was isolated from an infant aged 11 months in Yobe, Nigeria, who had onset of paralysis on November 10, 2012, and the latest environmental WPV3 isolate in Africa was from a sample collected in Lagos, Nigeria, on November 11, 2012 [9]. Last case of WPV1 was in 2014. The last case of cVDPV2 from an AFP case was in 2014 and last case of cVDPV2 from environmental sample was also in the same year. Although Kano State recorded all Five out of six WPV1 cases in Nigeria in 2014 [10] but, there has been a remarkable progress in reducing polio incidence by more 80% from 2012. One of the contributing factors to the progress is the improvement in the quality of routine immunization services. The highest numbers of polio cases were reported in 2011 and 2012 when the RI performance was 39% coverage by OPV3. The number of cases reduced when the RI performance increased to 97% OPV3 in 2014.

Authors' contributions
However, the quality of the administrative RI coverage is debatable due to RI 16% coverage reported by the National Indicator Survey (NICs for 2016). The introduction of IPV in the SIA in December 2014 and into the RI in March 2015 [11] might have contributed in increasing the population immunity and decline in WPV and cVDPV2. Several studies had demonstrated the use of IPV aids in preventing paralytic polio from wild or vaccine-derived type 2 polioviruses [12,13]. The quality of the SIAs improved from 2011 to 2017, this is evident by reduction in the number of LGA lots rejected to less than 80% by LQAs from 13% in 2011 to 1.2% in 2017. Periodic high-quality supplemental immunization campaigns to reach children who lack access to the routine immunization system, is one of the strategies to eradicate polio and similar infectious diseases such as measles [14].
Improvement of surveillance over the years has contributed in the progress made in polio eradication in Kano State. From the year 2010 to 2017 there was increase in AFP case detection and the two key AFP surveillance indicators have increased over the years, these key surveillance indicators are the stool adequacy and non-polio AFP rates. The NP AFP rate of ≥2/100,000 in children < 15 years is considered sensitive to detect WPV or cVDPV case if poliovirus is circulating. The second indicator is the collection of adequate stool specimen from ≥80% of patients with AFP. Adequacy refers to collection of two stool specimen ≥24 hours apart, within 14 days of paralysis onset, and arrival at a WHOaccredited laboratory in good condition [15]. Kano State had achieved both indicators over the years. However, the persistent reporting of polio compatible cases indicates surveillance gap, this underscores the need to be vigilant at enhancing the AFP surveillance in order to maintain the progress made in Polio eradication in Kano State. Environmental surveillance in Nigeria was piloted in 2011 in Kano State [16]. No WPV or cVDPV2 has been isolated since 2014. The last WPV3 and WPV1 were isolated in 2012 while the last cVDPV2 were isolated in 2014 in which 15 cVDPV 2 were isolated. These might indicate a surveillance gaps and calls for more vigilance. The finding of high number of cVDPV2 in 2014 is an indicator of low routine immunization coverage. Regular micro plan updates, and use of innovations such as the tracking of vaccination teams has help in addressing the problem of target population of children younger than 5 years.
Thanks to the efforts, the estimated target population was readjusted to three million children (from the six million projected from 2016 Census results) this correction brought about a better planned SIAs and reaching a realistic target. The quality of SIAs in Kano has greatly improved because of multiple simultaneous interventions in the form of timely release of funds, quality vaccination team selection, use of data for action and involvement of traditional and religious leaders in creating awareness about immunization and resolving noncompliance. Importantly, the introduction and scale up of Directly Observed Oral Polio Vaccination (DOPV) a vaccination strategy outside the households where male supervisors observe the administration of drops of OPV to each child, as precaution against teams who only mark the child´s finger.
Other innovations health camps, (i.e. where people receive free health services for minor ailment as well as immunization for children younger than five). The systematic engagement of Quranic teachers and Nomadic population leaders popularly called Ardos, data review and harmonization at the LGA level on the 6th day of the campaign, use of polio survivor groups for immunization and communication, engagement with religious leaders, use of community clowns and local theaters for communication, and distribution of "pluses" (e.g., whistles, balloons) to attract children, tracking of Internally Displaced Persons( IDPs) all contributed to improving the quality of campaigns in the state. The massive recruitment of health care workers capacity which include WHO surge staff, cluster